Bye-bye: Chris Moyles is to leave his Radio 1 morning slot. Photograph: Beretta/Sims / Rex Features

Ben Cooper, the controller of Radio 1, is a man with a fitting job title. To judge from his recent pronouncements, he would like to rigidly control who does – and who doesn't – listen to his station. Last Wednesday, Radio 1's longest-serving breakfast presenter, 38-year-old Chris Moyles, announced on air to his 7 million listeners that he will shortly be standing down to make way for a DJ 11 years his junior, Nick Grimshaw.

Moyles's crime? Having a million listeners in the 45-54 age bracket, something which Cooper is none too happy about. Over the past three years, the average age of Radio 1 listeners has, apparently, crept up from 31 to 32; Cooper wants it to be below 30, and to this end has set about ditching many of the station's more venerable fixtures (Judge Jules, another long-serving presenter, was an earlier casualty).

Radio 1 listeners, Cooper complained, are reluctant to graduate to more age-appropriate stations, such as Radio 2. "We have what I call 'festival dad'," he says, "who refuses to grow up and will now take his family to hear new music at festivals."

To be fair to Cooper, he is taking his cue from the BBC Trust, which wants there to be a clear gap between the target audiences of Radio 1 and Radio 2, to "make room for the commercial sector". Still, his words, intentionally or not, conjure up a rather strange idea: that taste should be pegged to how old you are, and that there are certain types of cultural consumption that are suitable only for particular age groups.

Of course, it is inevitable that different demographics lean towards different forms of culture. Audiences at Covent Garden will always be largely grey-haired, just as grime gigs will always be redoubts of the pierced and tattooed. Expecting taste to vary with age is reasonable enough. What's not reasonable is suggesting that this fact has some kind of moral basis, that people have an obligation, culturally, to "act their age".

Such a view evokes a depressingly straitjacketed idea of the average person's cultural evolution. You can just see it: a life spent dutifully "graduating" to the next station or channel, the next activity, when the appropriate milestone is reached. When, exactly, should you go from being an edgy festivalgoer into "new music" (note how Cooper makes a penchant for novelty sound almost dodgy, as if it were on a par with class-A drugs), to being an armchair devotee of recycled pop?

The implication is that, at around the time people have children, their curiosity will atrophy and they will effectively say: "Right, I know what I like now, and I just want to listen to it, again and again." (In other words, a life of Radio 2 and Take That reunion concerts beckons.)

And what about further down the line? Are we to infer that, as the wrinkles set in, you should cross another threshold and start listening to classical music, attending ballet and the theatre? When does Radio 4 enter the picture? To be saved for a slow-burn retirement of Gardeners' Question Time and You and Yours?

The point, of course, is that taste doesn't work like this, and nor should it be expected to. Why can't a 15-year-old like Wagner? Why can't grandad keep up with the latest trends in drum'n'bass? To expect the aesthetic preferences of the generations to have impermeable walls around them is to have frustratingly low expectations of what people are capable of.

It's to confine cultural life to a landscape of perpetually limited horizons, where people only ever desire to experience what's most "relevant" to them. Yet one of the great joys of art is precisely its ability to take people out of their immediate existences, to make them aware of lives different from their own. Age is one aspect of this. Are we to say that King Lear isn't a play for teenagers, because it deals with issues of ageing and dementia? Or that films such as Kidulthood or Plan B's Ill Manors are only for the under-25s?

Moreover, this kind of age-related pigeonholing is a recipe for ever greater generational friction and isolation. Ours is a society helplessly in thrall to the notion that age matters, that how old a person is says something essential about who they are. At one end of the spectrum, youth is fetishised, vaunted, glamorised.

Broadcasters and the press see it as essential to attract ever younger audiences and readers; political parties chase the "youth vote" (and appoint youthful-looking leaders in the hope of securing it); fortunes are spent on gym memberships and plastic surgery in a doomed attempt to make youth persist into middle age.

At the same time, the old are stigmatised, cast off, as if, as Martin Amis pointed out a couple of years ago, they were gatecrashers at a party "stinking up the place". They are turfed out of jobs (not that the young are getting much of a look-in there either), banished from our screens, and even increasingly denied the one advantage that has historically been conferred upon them – the possession of wisdom.

For the truth of the matter is that, while age is an indisputable physical fact, in all its other manifestations it is a social construct, a fabrication. The idea, for example, that there's an intermediate stage between childhood and adulthood – known as being a teenager – barely existed before the 20th century. Being young just meant not being an adult yet.

All such categories are little more than advertising contrivances, aimed at engendering a false sense of group identity, the better to facilitate the selling of products. The more pieces into which society can be sliced, after all, the better it serves the ends of consumerism, because each segment requires its own products and entertainments, to be discarded once the next stage is reached. (Attaching numbers to new technologies – the Mach3 razor or the iPhone 4 – is a related strategy, creating an expectation of necessary graduation.)

Ben Cooper is a self-professed Reithian, which is to say, he believes a public broadcaster has a duty to shape and educate society. One sensible way for the BBC to set about doing this would be to resist the temptation to age-bracket its content.

Target audiences should be dispensed with. Why does it matter if 50-year-olds like Chris Moyles? Of course, combating the ageist proclivities of our society is no easy task, because such views are deeply ingrained. But a good way to start would be to banish all suggestions that people need to grow up. "Festival dad" should be given not a slap down, but a slap on the back.